CONCHOLOGIA CESTRICA. 75 
DIAGRAM OF THE GENERA, AND SPECIES, OF THE FAMILIES VIVI- 
PARID, VALVATID#, AMNICOLIDZ, AND STREPOMATID. 
FaMILy. GENERA. SPECIES. 
MELANTHO. decisa. 
VIVIPARID#. { LIopPLax. sub-carinata. 
VALVATID-. VALVATA. tricarinata. 
: limosa, 
AMNICOLA. decisa, 
grana. 
AMNICOLID. BYTHINELLA. Nickliniana, 
lapidaria, 
PoMATIOPSIS. { lecticw 
SomMATOGYRUS. altilis. 
; Virginica, 
STREPOMATID. Gontozasis. var. multilineata. 
ANCULOSA. dissimilis. 
Sub-genus MELANTHO, Bowpircu, 1822. 
Animal of Melantho.—([W. G. B.] 
Fig, 152, 

Shell, thick, solid, ovate imperforate; whorls rounded, 
smooth; peristome simple, continuous. 
Animal, with the foot broad, and thin, produced 
beyond the rostrum, which is short and truncated; 
operculum concentric. 
M. decisa, Say. 
Paludina decisa, Say, Nich. Encyc., 1st Amer. Ecit., 
1817. 
Shell, elongate ovate; whorls 4, wrinkled across, and 
with minute revolving striz; aperture ovate, more than 
half the length of the last whorl; epidermis green; 
